PACCAR MX (2004 Emissions) Fault Code: P1055 Retarder Switches – Data Erratic, Intermittent, or Incorrect

SET CONDITIONS:
The PCI ECU (D420) receives a CAN message with an invalid position of the retarder switch.

DIAGNOSTIC CONDITION:
This diagnostic runs continuously when the ignition is on.

RESET CONDITION:
This DTC changes to inactive when the fault is no longer detected.

POSSIBLE CAUSES:
Mechanical failure or damage to the retarder switch

ADDITIONAL INFORMATION:
The retarder is a wear-resistant continuous brake. It is primarily intended for use in prolonged braking, for example when decelerating from high speed on a level road or when driving downhill.